Tool/software:
In our project at output of our buck converter application there is chances of getting High voltage to avoid this high voltage to enter into buck input rail we have added diode in this path and to avoid voltage drop due to diode we have taken feedback after diode and to protect FB pin we have added another diode and zener diode in parallel. You can see this configuration in below :
Vin Typ 12V
Vin min 10.8V
vin max 13.2V
vout 10V
L 18uH
Ron 30.1K
RF1 24.8K
RF2 3.4K
Ra 25K
CA 4nF
CB 2 nf
Iout 0.4A
What I observed when my conversion ration goes on decreasing I have more voltage dip like at 13.2V and 10V output everything works fine. and at 10.8V input and 10V output I have larger voltage dip during loaded 0.4A.also at 10.8V and 10V (actual 8.60), 400mA output I observed my feedback pin voltage is 1.052 so regulation is not working as expected. I think this is probably due to loss in diode during on and off cycle. Is there any way where I could estimate required diode forward drop without dipping voltage ? as without diode at output everything works as expected.
I have tested this circuit with another buck converter LMR14006Y and there it works fine with diode. What do you think could be cause of this in this buck converter(LM5163).
